1. Field of the Invention
The present invention relates to a control technique of an image processing apparatus.
2. Description of the Related Art
A multi function peripheral and a multi function printer (MFP) are examples of an image processing apparatus. In general, an image processing apparatus includes a main unit and an operations unit. The operations unit is a unit with which a user can operate the image processing apparatus. For example, an operations unit may include a display that displays an operations screen, and a key pad for key input operation. For such an image processing apparatus, a configuration may be considered such that an operations unit is separated from a main unit. With such a configuration, even if the processing load of the main unit is heavy, the latency of a response to an input operation can be avoided. In the operations unit, an independent operating system (OS), such as the Android OS, is installed. The operations unit can operate independently from the main unit.
In order to facilitate transferability of image data or a program, the operations unit is provided with a slot for a memory card or the like. With such a configuration, a memory card or the like, as an external storage device, may be detachably attached to the operations unit.
A device (e.g., the main unit or the operations unit) that uses the external storage device may depend on usage of the external storage device.
Examples of the use for which the main unit uses the external storage device may include the following:                to print out a file stored in the external storage device;        to store a scanned image in the external storage device;        to store a result of self-diagnosis by the main unit; and        to update an application of the main unit by using the external storage unit.        
Examples of the use for which the operations unit uses the external storage device may include the following:                to store an image edited by the operations unit in the external storage device;        to update an application of the operations unit by using the external storage device;        to store a mail received by the operations unit in the external storage device;        to view an image file stored in the external storage device by using the operations unit; and        to store a log of operation of the operations unit in the external storage device.        
An OS executed by the main unit may be different from an OS executed by the operations unit. It may not be efficient to provide a file sharing function or the like for such an embedded system. Accordingly, for each time the external storage device is used, connection to (or mounting of) the external storage device may be switched for a device (e.g., the main unit or the operations unit) that uses the external device.
Patent Document 1 (Japanese Patent No. 4135735) discloses a method of switching an operation mode of an image processing apparatus. According to the disclosed method, upon insertion of a medium, a state of an original document is detected and a determination is made as to whether a file is stored in the medium, and an operation mode of the image processing apparatus is switched to a scanning mode or a print mode. In this manner, an attempt has been made to improve operability of the image processing apparatus.